Pneumonia is an inflammation of the lungs caused by a bacterial, viral, or fungal infection.

Alternative Names

Pneumonitis; Bronchopneumonia; Community-acquired pneumonia

Causes, incidence, and risk factors

Pneumonia is a very common, often serious illness that affects about 3-4 million people each year in the United States. Many different organisms can cause pneumonia, including bacteria, viruses, and fungi. Bacterial pneumonias tend to be the most serious. In adults, bacteria are the most common cause, and of these Streptococcus pneumoniae (pneumococcus) is the most common. Respiratory viruses are the most common causes of pneumonia in young children, peaking between the ages of 2 and 3. By school age, the bacterium Mycoplasma pneumoniae becomes more common. In some people, particularly the elderly and those who are debilitated, pneumonia may follow influenza . Pneumonia is classified according to a number of different systems. One classification system divides pneumonia into "community-acquired" (pneumonia contracted outside of a health-care institution) and "hospital-acquired" (acquired in a hospital or other long-term health care facility). S. pneumoniae is the most common form of community-acquired pneumonia. Hospital-acquired pneumonia tends to be more serious because the patient's defense mechanisms against infection are often impaired when someone is hospitalized, due to the condition that initially required treatment . In addition, there is a greater possibility of infection with bacteria that are resistant to antibiotics. Other classifications of pneumonia include:

aspiration pneumonia

atypical pneumonia

bacterial pneumonia

CMV pneumonia

hospital-acquired pneumonia

Legionella pneumonia

Mycoplasma pneumonia (

walking pneumonia )

necrotizing pneumonia

pediatric pneumonia

Pneumocystis carinii

pneumonia

pneumonia in immunocompromised host

pneumonia with lung abscess

pyogenic pneumonia

viral pneumonia

Signs and tests

Crackles are heard when listening to the chest with a stethoscope (

auscultation ). Other abnormal breathing sounds may also be heard. Tests include:

chest X-ray

Gram's stain and culture of the sputum

CBC

arterial blood gases

This disease may also alter the results of the following tests:

thoracic CT

routine sputum culture

pulmonary ventilation/perfusion scan

pleural fluid culture

lung needle biopsy

Treatment

If the cause is bacterial, the goal of treatment is to cure the infection with antibiotics. However, if the pneumonia is caused by a virus, antibiotics will NOT be effective.

Supportive therapy includes oxygen and respiratory treatments to remove secretions, if needed.

Expectations (prognosis)

Most patients will respond to treatment and improve within two weeks. Elderly or debilitated patients who fail to respond to treatment may die from respiratory failure.

Complications

acute

respiratory

failure

death

empyema

Calling your health care provider

Call your health care provider if symptoms suggesting pneumonia develop.

Prevention

Vaccination can help prevent some types of pneumonia in children and at-risk adults (such as the elderly). These include:

pneumococcal vaccine (Pneumovax (R)

(prevents pneumonia caused by

Streptococcus pneumoniae )

flu vaccine

Hib vaccine

(prevents pneumonia from

Haemophilus influenzae type b) Coughing and deep breathing may help prevent some forms of hospital-acquired pneumonia . See also the prevention steps listed under specific types of pneumonia.